Telephone-exchange system.



E. E. CLEMENT.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED DEO.28, 1905.

Patented July 28, 19%

3 BHEETBBHEET 1.

Suoewtoz Wilma:

E. E. CLEMENT.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED nso.2s,19o5.

1,105,589. Patented July 28, 1914.

3 BHEETSSHEET 2.

El" L a L". 1

M W F Snuentoz Witnesses E. E. CLEMENT. .TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED DBO.28,1905.

1,1 05,589. Patented July 28,1914.

3 SHBETB8HEET 3.

awcwioz mmfw W N 7772/14.

iinrii nn srarns reruns? crimes.

EDWARD E. CLEMENT, WASEINGIOK, DISTRICT OF COLUMBEA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO FREDERICK C. STEVENS, OF ATTICA, NEW YORK.

JEELEPHONE-EXCHANGE' SYSTEM.

mousse.

To all whom it in (17 concern .2 7

Be it known that I, lflnuxuui E. CLEMENT, a citizen of the United States, residing at \Vashington, in the District. of Columbia, have invented certain new and useful Improvements in TelephonoExchange Systoms, of which the following is a spec1fication, reference being had therein to the accompanying drawings.

My invention relates to telephone exchange systems, and hasfor it object the provision of means whereby calling sub-- scribers may be answered by operators, the wishe ofthc calling subscribers conununi: catrd in part or in whole by signals, and the desired connections,effected by means of automatic mechanism controlled from the subscribefs station; I

The invention contemplates the use of a smaller number of answering jacks and of a. very much smaller number of operators than are now employed in connection with manual switchboards. Certain mechanisms are provided which will be referred to as primary selectors, wvhich' are themselves connected to the answering jacks, and which contain terminals of the subscribers lines. Associated with each answering jack is a pair of indicators, and when a subscriber calls and his line has been picked up by the primary selector of any jack, he sets these indicators to the thousands and hundreds numerals'of the number he wants, by manipulating a suitable key or sender at his substation. Itshould be stated that this sender does no more than to make and break the metallic circuit, there being no grounds outside of the central office. f V] hen the operator perceives the indicators set to a number, as for example 24, she plugs into the line-jack to which these indicators belong, and with the other plug of the pair in use she plugs into the trunk-jack of a group numbered 24 and which is connected to an automatic connector switch containing terminal to subscribers lines numbered from 2400 'toQiJtl. The operator thus does not speak to the subscriber, and soon as the latter receives an ii'iilication which I provide to show he is connected to the automatic switch, h again works his sender, and thereby works the switch, to secure connection with the desired line.

Specification of Letters Patent.

1 larly to Fig. 1,

Patented July 28,1914.

Application filed December 28, 3,805. Serial No. 293,630,

My invention is illustrated the accompanying drawings, wherein- Figure 1 is a diagramishowing a subscribers station and line-circuit, primary selector switch mechanism with answering terminals and a cord-circuit at the central office. Fig. 2 shows a trunk leading to an automatic connector switch, and a subscribers line having terminals in the banks thereof. Fig. 3 shows a type of automatic connector switch which may be employed in this system, Fig, 4 is a detail bottom-plan view thereof.

Referring to the drawings, and particu- A is the'subscribers station connected to the central oflice by line-wires 1 and 2, which terminate'in contacts 12, n, of the cutoff relay N, throughwhich they are normally connected, the first to the line-relay 1M, andthe second to ground tlirouglrwire At the subscribers station I place the usual apparatus employed in common battery systems, viz., ,receiver,' transmitter, ringer and condenser, with a switch-hook to open and close the metallic circuit through the talking set. I also place therea-t two special pieces of apparatus which, however, may. be dispensed with where the subscriber is possessed of suflicient skill. Thefirst of these is a key K for sending the numbers wanted and thereby manipulating the mechanism at the central office. The second is a special signal device Q, having a pair of magnets and an armature like those of the ordinary polarized ringer, but with a small target on the end of the clapper rod instead of the clapper. This signal device is connected in series with the talking set, and is low-Wound, but may be connected inshunt therewith, and in that case would be very high-wound. Its purpose is to inform the subscriber after he has called, of the fact that his call has received attentiomor that his line is connected'at the central oflice, so that he can proceed to signal. y

W'hen the cutoff relay N is energized, it pulls in the contacts n, n, and connectsvthe line-wires12 onto theextension wires 5 and 4, terminating in contacts 0, 0, of a primary selector switch 0. The subscribers lines have no other answering terminals than the contacts 0, 0, and the functions of the primary selector switch which contains the an swerings terminals of one hundred lines, is to pick up any one of these when calling, and connect the same onto the jack J, forming the trunk terminal for the switch 0. This jack J has spring contacts j j, a resting anvil for the former j, ant a sleeve contact, 7' The purpose of the resting anvil, j', is to permit'of cutting of? certain circuitsin the jack. Obviously, however, this maybe accomplished by the use of a cut-off relay and the jack thereby simplified, if desired. The springs of the jack are connected respectively to the wires 10 and 9, leading to what I may term bus contacts 0 and 0 in the bank of the primal? selector 0. These bus-contacts are. pre erably annular combs or rings having inwardly projecting radial teeth, one tooth on each ring corresponding with and lying opposite each contact 0 or 0. Above each contact 0, and corresponding to its line, is a pair of test contacts 0", 0 the function of which will presently appear. The operating parts of the primary selector are carried upon and actuated by a spindle 0, which I have shown constantl driven through a belt and pulley. ()n tliis spindle is carried a hub 0 having a radial arm 0 formin the tube for a magnet spool with two winc ings 0, 0*". In this tube is fitted to slide the combination core and plug 0 0 the core portion being of soft iron, and the plug portion being of insulating material, such'as hard rubber. The two are secured together in any suitable manner, as by means of a threaded stud on the end of the core tapped into the plug. The plug is normally retracted by a spring within a cap on the outer spool-head of the magnet or solenoid, and this retraction forces the inner end ot the core to engage a notch in the spindle 0, whereby the tube 0 nd its connected parts are normally carrir i around by thev spindle in its motion. The windings 0, 0 on the magnet are (OHUCt'lCd to spring-contact wipers 0", 0" which travel over the series of line test contacts 0, 0 ()n the other side each winding is grounded. When any line relay M is energized it puts battery through the wii (3 on the wire 7 to contact 0*, and thence when the spring 0 comes around to that ontact. i hrnngh said spring to the magnet winding 0 and ground. This pulls out the core 0", projecting the plug 0 between the springs 0 o and closing them upon the line springs 0, 0. The line isthen roollt'l'ttfl by our o't wires 4, 5, it). and ii to the contact sprin s 2. w re 10 being also conne tral throu the anvil i and wire 11 to main halter l3 through an inductive resistance M.

if indicates the main attery Wire or bus, which supplies the Vlli'l() l\' pieces of appa ratus. At the same time the wire 9 is conthence by wire 14 to the magnet M and ground. A complete path for the main battery can therefore be traced out through the wires 10, 4 and 2 to the substation and back over the wires 1, 5, 9, 13 and 14 to ground through magnet M", which becomes energized and pulls up its armature, the first effect of which is to connect the battery extension wire 15 with the wire 8 leading to the holding contact 0 and thence through the spring 0 to the winding 0 of the primary selector, and to ground. The winding 0 thereafter maintains the core 0 in position, the other winding 0 losing current, as soon as the line-relay M is cut off, which occurs as soon as the condition to which I have referred is established; for a part of the current flowing over wires 10, land 2 is diverted to ground through the cutofi' relay N. Moreover, it is imperative that the contact 0 be rendered dead during continued operation, for the reason that this contact is supposed to be only one of a plu rality of multiple-contacts to which the wire 7 is connected. In other words, this wire 7 representing the line 12, and also-the line extensions 54., is multipled into a number of the primary selectors 0, so that the first primary selector which happens to be idle will pick up the calling line. Ten of these primary selector switches to One hundred lines at present appears to be about the proper proportion, so each line will have ten multiples. Now, if a contact 0 were to be left alive for any length of time, with its potential raised, then the potential of all of its multiples would also be raised, and the other switches would get false signals so that more than one of them might stop on the same line. As these multiples are on the line side only, however, they can be cut oil after the switch has plugged in on the line calling, provided that another controlling means associated with the switch itself is then rendered active. This comprises the second coil or winding 0 and its circuit through the wiper 0" and the ring contact- 0 connected through wire 8 to the front. contact of the relay M which becomes energized by return current from the line through the wires 9 and 13. the switch-arrn m, and the wire 14 to ground, as soon as the line is put. on the wires 9-10. This controlling circuit being purely local to the switch, maintains the same in conne tion with the line until the end of the connection, without risk of interference with other switches.

Associated with each spring jack .l is an indicating device I, having a pair of oloctro magnets i, i and a pair of indicating wheels 2?. i supported on a pair of shafts or spur 2'. I do not illustrate the details ot this indicator as such devices are Welhknown nccted through wire 13 to a switch-arm m, i

in the art oi signaling. and in itself, that is the battery wire 12,

magnet Z.

operated will to say in its construction, it forms no part of my present invention. The numberwhecl v controlled by the clectro-magnet 2', through a pawl working in a ratchet wheel attached to the indicator; and the numberwheel i similarly controlled by the electro- This indicating device may be ctmtrolled by the subscriber to show the thousands and hundreds digits of the line he wants, whereby the operator may at once connect him to a connector switch having terminals of the desired hundred, only one set of these switches being therefore re quired, and great economy both in the amount of apparatus and in operating expenso being effected.

\Vhen a subscriber calls, the first thing that happens is the connection of his line to an answering-jack J, as I have already pointed out. By tracing the battery cir cuits it will be observed that battery being normally connected to the No. 1 side of his line, is thereafter connected to the N0. 2 side of line, or the direction of current flow in the line is reversed. The signal Q is thereupon effectively energized, and throws up its target to show the subscriber that he may proceed with the signaling. By the manipulation of the key K, he then sends the first two digits of the whole number wanted, the same being received first on the indicator wheel 2", and the second being received by the wheel 5. The operator percciiing this number set up, at once plugs the subscriber through onto a connector s itch-trunk bearing that number, all of the trunk multiples in front of each operator being divided into groups, and marked from 1 to 05). The means by which the indicators are successively brought into circuit, and

now be described.

m, m are two switch-arms connected and moving together, and each having three con tact points, on the first of which it normally rests. The magnet- M steps these switch arms around through a pawl and ratchet .lnwhanisln, a suitable detent being provided, which is controlled by the magnet M, which acts. to release the arms and restore the entire indicator mechanism when the answerintt hlug P is placed in the answering jack J.

When the line 1 2 becomes connected hrough the wires 9-10 with the jack J, current flows from the battery B through magnet M-, and wire 11 to the spring j of the jack and so through the wire out to the line-wire 2 to the substation A, through the talking set thereat. and back through wires 1, 9 and 13 to the switclrarm m and so by wire It to the magnet M and ground. The magnet M then attracting its armature and so connecting the wire 15 to the wire 8, in order to maintain the primary selector switch in the position it has assumed; and the wire 15 isalso connected to the wire 16. and then e to wires 18 and Q0, the former going to the switch-arm m and thence by 19 to the indicator i and ground; and the wire 2') gcing to the contact 8' of the solenoid relay S, the twin contact 8 being connected by wire 21 to the magnet M". which control the switclrarm m, m and ground. These springs are normally separated. and the solenoid is so constructed that it will pull up its core a very quickly, but it will permit it to fall "cry slowly. This end is attained by making the core slide like a, plunger in the tube of the solenoid, the upper end of which is fitted with a valve shown in dotted lines, and consisting of a small ball in a conical seat, opening through a central channel into the tube of the solenoid. hen the core a is drawn up the air is expellcd freely, raising the ball from its seat, but when the solenoid is decnergized the ball falls into its seat and prevents the ingress of air in any quantity, the arrangement being similar to wellknown dashpots as used in door closers and the like. The solenoid winding is connected on one side to ground and on the other through wire 17 to the back contact of re lay M In order to prevent the solenoid from being constantly energized when the apparatus is idle, I cause the magnet M to control the continuity of the battery circuit 12-l5 closing the same whcn it is energized only. The first flow of current through the wire 9 and magnet M produces no effect, because the springs s, s are open, and the magnet i merely energized to pull up its armature, without moving the wheel 1', which I should remark is stepped around on the back strokeor retraction of the armature. The current now being reversed on the line, as previously pointed out, the magnet Q shows its target, and the subscriber taps the key as many times as there are units in the first digit to be sent. Assuming for example that the number he wants is 4468, he taps the key four times and then leaves it closed for a brief interval. Each lap breaks the circuit and permits the armature of relay M to fall back. At the first falling back, this armature closes the circuit of the solenoid S as follows: B, 12, 15, 17, S and ground.

The solenoid immediately pulls up and in so doingimomentarily closes the springs 8, 8 but this produces no etl'cct, since the wire is (in the front contact of the relay, which is opened when the eolenoid pulls up. Each time the armature of the relay falls back and pulls up again, the battery circuit through the wires 18 and 19 to the magnet i is broken, and this magnet therefore steps around its wheel 2" four step During the four breaks produced in the line, the solenoid core 8 has remained up above the yery slowly,

springs, because as I have stated it retracts and has not time to reach the springs during the brief intervals between the excursions of the relay armature. At the end of the first group of impulses, however, the relay M remains energized, and the solenoil wire 17 is cut, oil for a long; enough time to permit the core 3 to pass the springs and complete the following circuit momentarily: B, 12, 15, 1(3, '20, s, a, 21, M and ground. The magnet M thereupon attracts and releases its armature. moving; the switch'arms m. m, one step, so that they rest upon the second conta ts in their respective sets. The arm in. does not produce any change in conditions, since the wire 13 is connected to both the tirst and sec nd contacts; but the arm in, pzHsw trom the c ntact forming the terminal ot wire 19 to the contact connected by wire to the magnet i, which is the second indicator magnet. The subscriber now makes a second group of breaks, whereupon the former operation is repeated, the magnet z" steps around the wheel 2' to the fourth place, so that the two wheels together show the number 44, preferably through a little window in front of them. At the end of this group of breaks the subscriber leaves the key closed, the solenoid S lets go its core, the springs s, s are closed together for the second time, the magnet M gets another momentary impulse of current, and the switch-arms 'm, m are stepped around once more. The arm m now passes on to a third contact forming a terminal of wire 23, which puts the battery wire 12 directly on to the magnet M through wire 14, and maintains thesame energized until the plug P is inserted. The arm'm passes on to a blank, so that the indicators are entirely disconnectt l.

As soon as the operator perceives the number-wheels set, she knows that a line is connected to the corresponding jack, and that the subscriber wishes to be connected with some other subscriber whose number commences with 44. She thereupon inserts the plug 1 into the jack J, and the plug 1 into the trunk-jack J (see Fig. 2) of the 44th group. The trunk-wires 24 and 25 from this jack lead to an automatic connector switch C, containing terminals of all the lines from 4400 to 4499.

Associated withthc cord-circuits 26, 27, .28. 29, is a pair cit solenoid relays S, S constructed in the same manner as the solenoid S, as regards their cores, and the solenoid 3 having also a similar pair of springs a, s". The solenoid S however, has five springs, s s" .ss s, of which the last four are normally held closed together, and the first named is left open, the insulating head on the lower end of the core being adjusted to maintain this condition when the apparatus is idle. \Vhen the solenoid is energized, however, springs s" are closed together and the others are left individually open. Also associated with the cord-circuit, or with the ;lll VJt*lit1: end ot it, QtJ QS, is a pair of relays S". S, which are bridged across the core with the battery 1) between them. The armature of relay S is connected by wire to the battery wire 12, and when attracted connects the same through wire 31. to the armature of the relay The back contact of the latter is connected by wire 39 to a supervisory lamp L, and also by a wire 36. through wire 38 to the solenoid winding; S, through wire 39 to the spring a of the other solenoid; the wire 36 is also connected through wire 37 to the spring a" of the same set. The spring a is connected through wire it) to the sleeve of the plug 1, this plugbeing a three-way plug with tip, ring; and sleeve contacts; tip and ring contacts constituting the terminal for the talking circuit, wires 26 and Q8. The spring s is connected by wire 11 to the cordconductor 29, and the spring 8 by wire 42 to the cord-conductor 27. The cord-conductor 29 is also connected through wire to the spring 8 of solenoid S, the other spring of this pair going by wire 34; to the wire 33, which terminates in tle front con tact of the relay S, and is also connected to the winding of the solenoid S The operation of these parts will be stated later. Before proceeding thereto I will describe the switch-circuits in Fig. 2, and the mechanism thereof in Figs. 3 and 4', the last first.

ttll til'lltg to Figs. 3 and 4, I have therein illustrated a typical connector switch. comprising" a frame 0. constitutiiug an tip-standing tlangc around a flat plate (2", and carrying at its lower end the posts 0 upon which are mounted line and test contacts 1:. Joun naled in the frame vertically, so that it. may be moved up and down and also rotated therein, is a spindle (1 carryingat its lower end the wipers c, c. The wiper 6' can be dispensed with, in the present case. as it will be observed it only use one pair in the diagram, but the lower wiper c and its cow tarts are also provided, and it not employed for testing are found useful for attaching line meters or other ap 'iaratus. The spindle is fitted with a pair of ratchets 0 c. the former consisting of a series of circular teeth up and down the spindle, and the lat ter of a broad taced ratchet wheel having long straight teeth extending parallel with the spindle, Cooperating with these ratchet 4 is a common pivoted detent 0, having an arm 0 engaging the ratchet a second arm o engaging the ratchetc, and an upstanding bell-crank arm (2 carrying a pin adapted to be engaged by the latch on the armature c of the release magnet 11'. 'hen the armature is attracted the latch 0" is thrown forward until it engages the Ipin, then upon retracting it pulls over the ell-crank, leaving the arms and c and permitting the spindle to be restored, the latch passing off the, pin at the end of its movement, after the spindle has gone back to zero, which takes very little time. The spindle is stepped up by means of a pawl c", on an armature 0, controlled by What I ehall call the vertical magnet V. It is stepped around by means of a ratchet 0 on the armature 0 of what I shall call the ro-. tary magnet R. This magnet also controls the pair of contacts 0 which are connected in its own circuit, so as to make it a vibrator or buzzer. The armature e carries a projecting arm 0, which passes down into position to engage the armature 0 of what I shall call a private magnet T. The armature of this magnet also carries an escapement t, and controls contact springs lettered in the diagram. The escapement permits the movement one step at a time of what I shall call the side switch U, which is pivoted at u, and is restored to the position shown in Fig. 3, by means of a bell-crank lever u when the switch spindle is down, the upper or short arm of this lever engaging beneath the ratchet wheel 0 and the end of the long arm engaging the upper end of the switch-- lever. This side switch to which I have referred as U, has four arms shown in the diagram, Fig. 2, as u, if, u u, all of which move together and are attached to the common block of insulation M The spindle is restored and maintained in the position shown in Fig. 3 by a coil spring housed in the cap one end of the spring being at tachcd to the spindle and the other end to the arm the end of which is perforated to receive the post upon which it travels up and down. A stop arm 0 is adjustably mounted on the spindle below the spring arm. so as to determine the proper normal position for the spindle and the wipers.

Referring now to Fig. 2. V and R are what I shall call the vertical and rotary relays. respectively bridged across the switchtrunk and grounded between their windings. The relay V controls the contacts 0, v, and relay It the contacts 2", 1", a pair of intermediate ground contacts 9 cooperating with 1 and r. The parts in Fig. 2 being all lettered the same as in Fig. 3, further description thereof is unnecessary, and the nature of the circuits will sufliciently appear from the statement of operation, which I will now give.

The operation of calling and of indicating the first two digits of the number wanted, has lJIcll given. Proceeding, therefore. from that point. I will remark merely that when the plug 1 is inserted a clear through circuit from the line to the cord is obtained. The cut-elf relay N in putting the Wires l2 i on to the wires 9l0, disconnects the linel of solenoid S relay M, and the last step of the writ .1- arms m, m disconnects the imignriv i l from wire 9 and puts it on to wire 23. where it remains preferably until the plug 1 is finally pulled. As soon as this plug is inserted. a circuit is completed as follows: battery It, 12, 30, 31, 32, 36, 37, a. s. 40, sleeve of plug P, jack thimble j 52, M and ground. According to this preferable mode of operation, w th the indicators and the magnet M cut oil during the connection, it is necessary that the magnet M should release the indicators upon the back stroke. that is only by pulling up and then releasing lis armature. This sort of a release is illustrated in Fig. 3, where the magnet It performs a shear function in a similar manner. Thus. mien the plug is inserted. the release magnet is energized, but nothing further occurs. it is possible, however, for the two renuiining digits of t he number to be taken on the indicators, or for that matter it olniousl; involves no departure from my invention to multiply the number of :ter wheels and the number of switclecontacts contmling them, so that all the digits will come in and be received in due order. The plug being in. the magnet hl is of course cut oil. and cur-- rent supply for the line and the i llljdli lay N then passes from the main batten way of wire 12 through the relay conductor 28, and so to wires 10, t and L. The subscriber at the same time gains con trol of the relay S and he proceeds to send the last two digits of the number wanted. which we have assumed to be The aruiw ture of the relay S being up as soon as. lhc plu is inserted. the solenoid takes currcnt. and pulling up its e opens the springs s, .9 8 and close thus completing the 'tollmving for inupulses to the irunlow'irc fill:

buttery li. lit, 30.31.31 :16, fla -1N. 4:2. tip of plug P. The first break of the group o ix in "ie next digit. muses.- the armatur of? relay t fall back. sending a pulse cl current n this circuit into wire 24. tl'n-ongh the branch and magnet V to ground. At the same time the same pulse goes through .Vll'ts 23 3 and 38 to the solenoid of S and ground. and this solenoid pulls up its core. n1omentarily closing the springs 8 a. but produw ing no effect thereby since their circuit is open through wire 33 and at the front contact of relay S The magnet of relay V becoming energized closes the following circa, V, 04, at. It.

cuit: g, t 61, f, if, (32. u, 72, battery B. Each time this occurs, that for each break at the key K, the vert magnet V in Figs. 2 and Z i energized to step up the switch spindle 1", one step. 3 there are six taps on the key. the wiper 1, goes up to the (Jtl; M. The pause which follows with the lin. closed, perndts the core to move all the very down,

closing the springs 8 8* together and sending a momentary pulse of current over the trunk 25 by the following path: B, 12, 30, a1, 33, 34, 8*, s s5, 41, 29, P, J, 25, 59, n nd ground. The relay R pulling up closes the following local circuit in the switch: g, 1", 68, T, 70, 72, and battery. The relay T thereupon pulls up, and as will be seen by reference to Fig. 3, steps the side switch arms around one step, thereby cutting off the magnet V, cutting on relav R, and through the arm a connecting the wire to the test wire 76. The next group of breaks at the key K also affects the vertical relay V in the same manner and over the same circuit, the local circuit, however, being now as fol lows: g, o, 61, t, t, 62, u, 51, R, 64, 65, 71, 72. B. The magnet R thereupon steps the spindle around until the wiper a rests on the No. 8 contact pair in the 6th row. The subscriber then removes his hand from the key, and the circuit remaining closed the solenoid is operated as before, sending another single pulse from the trunk 25 and through.wire 59 to rela R and ground. This closes the same local circuit as before through the relay T, which pulls up on the impulse and at the instant of pulling up closes the following test circuit: B, 72, R (release magnet) 73, 74, t, t 75, 76, a, (tip side).

If the. line wanted is busy it will have a ground on its tip side, either through a cordcircuit, relay S and a magnet M or a connector switch magnet ,In any such case the release magnet R will immediately work and send the switch back to zero before the talking circuit is completed by the last movement of the side switch. If the line is not busy, however, this does not occur, and the magnet T completes its movement, releasing the side switch U for the third time, and completing the talking circuit to the called line by way of wires 56, 78. 80, 57, 77, 79. The third motion of the switch arm a connects the wire 62 with the ringing relay wire 67, this relay R controlling the ringing key by which the generator D is connected to the wipers (T the same being simultaneously disconnected from the trunk wires 56 and 57. This ringing relay is operated by any number of short breaks which the subscriber chooses to send. If it is a party-line he may send 1, 2. 3 or 4 breaks, each one of which will work the ringing relay by working the vertical relay V.

Battery current is supplied to the called line for talking purposes through the following path: B, 72, T1. X, 57. 77, 79, out on the subscribers line, back on the tip side, 80, 78, 56, X and ground. Condensers C, C separate the trunk-circuits in order to prevent confusion during selection. A perfectly clean talking circuit is then provided with only one pair of condensers, and

l l l l l l l bridged battery feeding both ways. This is identically the same circuit which is now considered standard in manual switchboard installations. state that it is found advisable in practice to makc two back contacts for the armature of the relay S, in order that the wire 42 and conductor 27 may not be constantly crossed with the solenoid wire 35 and the lamp wire 32. Both of these are grounded, which would put a permanent ground on the tip side of the trunk. but if the wire 39 be made to terminate in a separate back contact, instead of being common with wire 36, this difiiculty is avoided. \V hen the subscribers have finished conversing, they hang up their telephones; the relay S thereupon lets go its armature, and the solenoid S loses current and for the first time since the actuation of the connection permits its core to fall all the way down. The springs s, s are thereupon forced apart, and the other springs a, s s 8 are all forced together. Current thereupon llows over both sides of the cord and both sides of the trunk as follows: B, 12,30,3132, 36, 37, a s, to conductor 27 and wire 24; also from s" to 8 conductor 29 and wire 25. From the wires 21 and the circuit is on both sides through branches 58 and 59 and relays V and R to ground. These relays pull up simultaneously, closing together the contacts a and 1', and thereby closing the release magnet circuit as follows: E, 72, B, 73, 69, r, o. 60, ground. The release magnet thereu on restores the switch. At the same time, 1 1e lamp L associated with the answering plug P glows. and the operator pulls the plugs P, l, whereupon the release magnet M sets back the indicators to zero, and as the line-circuit is broken at the subscribers station the magnet M then loses current, opening the circuit 8, deenergizing the solenoid 0, permitting the plug 0 to withdraw, and thereby releasing the primary selector 0, which resumes its travel over the line-contacts, and all is once more in condition to take another call.

Having thus described my invention what I claim and desire to secure by Letters Pat-- out is 1. In a telephone exchange system, a plurality of line circuits, circuit terminals for the lines, an indicating device associated with the circuit terminals, means adapted to automatically connect the same to a calling line in response to a call, means for controlling the same thereafter over the line, means' for manually initiating a connection and extending the same in accordance with the indications, and electromagnetically con.- trolled switching devices brought into con nection with the manual means for automatically completing the connection there after substantially as described.

2. in a telephone exchange system, a plu- In this connection I should rality of subscribers lines and connective apparatus therefor composed of separable elements as follows: answering terminals, indicators associated with said terminals, means adapted to automatically connect the same with the lines in response to calls thereover, means for thereafter controlling the same over the lines, manually operated devices for connecting the lines through one or more links in accordance with said indications, and automatic switches electromagnetically controlled therethrough to complete the connections, substantially 'as described.

3. In a telephone exchange system a plurality of subscribers lines, and connective apparatus therefor comprising the following instrumentalitie a number of answer ing terminals less than the number of lines, automatic means for connecting a calling line with an idle one of said terminals, :1 number indicator associated with each terminal, means for extending the connection in accordance with the indications thereof, and automatic means for completing the connection, substantially as described.

4-. In a telephone exchange system a pluialily'of subscribers lines and means for interconnecting the same comprising the following instrumentalities: a number of answering terminals less than the number of lines. automatic means for connecting a calling line with an idle terminal, an indi cator associated with each terminal. and adapted to be controlled through the calling line circuit, means for extending the connection in accordance with the indication when set, and automatic means for completing the connection, substantially as described.

5. In a telephone exchange system a plurality of lines and means for interconnecting the same comprising the following instrumentalities: a number of answering terminals less than the number of lilies, an indication set including a numerical indicator adapted to be controlled through the call ing line circuit and means for automatically connecting a calling line to an idle answer ing terminal. and adapted to be controlled over the calling line and connective apparalus adapted to be manually brought into association with the indication set, and thereafter to be automatically controlled through the calling line, substantially as de scr bed t ln atelcp n xchange system. a pile rality of lines and means for interconnecting the same comprising the following in stirunientalitics: a munber of answering terminals less than the number of lines, auto matic switching means responsive to calls over the lines for connecting a calling line with an idle "rninal, a numerical indi cater for each terminal, means for setting saidindicators controlled through the calling lines, and automatic switching appzn ratus adapted to be mallually brought into association with the answering terminal of a calling line and thereafter electromagnetically controlled to select, test and con nect with the line wanted, substantially as described.

7. In an automatic telephone. exchange system a plurality of lines and means fcr interconnecting the same comprising the following instrinnehtalities: a number of answering jacks less than the number of lines, an automatic primary selector switch adapted to be controlled by a line when calling and to connect the same to an Idle jack, an indicatorassociated with the iaclt and adapted to be brought under control of the line when so connected, a trunk line terminating in an automatic connector switch containing calling terminals of a plurality of the line circuits, a plug and cord for connecting said trunk to the answering jack of a calling line, and means for controlling said switch from the subscribens station, substantially as described.

8. In a telephone exchange system a pile rality of lines and means for interconncct ing the same comprising the following instrumentalities: a number of answering jacks less than the number of lines. a mum bcr indicator for each jack. means at each substation for operating said number indi cator, and connective circuits having plugs and automatic switches, the latter le s in number than the number of lines. and coir taining calling terminals of the various liue circuits. the plugs and switches so arranged that the answering jack of a calling line may be connected to a switch corresponding to the indication set. said switch thereafter being Controlled over the calling line to complete the connection, substantially as described.

9. in a telephone exchange system a plu rality of lines and means for interconnecting the same comprising the following instrumentalitics: a number of answering tcrmi nals less than the number of lines, an automatic primary selector switch adapted to be controlled by a calling line to connect the same with an idle answering terminal. a

.double digit number indicator associated with each terminal and adapted to be operated over the line to indicate the hundreds group in which the line wanted is found. a plug and cord-circuit and a p urality of am tomatic connector switches, each containing calling terminals for one hundred lines, said plu cord-circuit and switch being so arranged that a calling line may be connected to' the particular connector switch which contains the terminal of the line wanted, substantially as described.

10. In a telephone exchange system a pluill rality of lines and means tor interconnecting the same comprising the following instrumenialitics: a number of answering terminals less than the number of lines, a primary s-clcrtor switch adapted to be controlled by a calling line to connect the same with an idle answering terminal, a double-digit number indicator associated with each terminal and adapted to be operated over the line to indicate the hundreds group in which the line wanted is found, a plug and cord circuit and a plurality of automatic conncctcr switches, each containing calling terminals for one hundred lines, said plu cord-circuit and switch being so arrange that a calling line may be connected to the particular connector switch which contains the terminal of the line wanted, together with means whereby said switch may there after be controlled over the calling line to select the line wanted. substantially as described.

ll. In a telephone .exchange system a plurality of lines and means for interconnecting the same comprising the following instrumcntalities: a plurality of answering jacks le s than the number of lines, switching means automatically operated to connect a calling line with an idle answering jack, a hundreds indicator associated with each jack and controlled over a calling line, connective circuits comprising answering plugs and automatic connector switches, each containing the calling terminals of some particular one hundred lines, and a supervisory signal associated with each answering plug and controllable through the plug circuit, substantially as described.

12. In a telephone exchange system a plurality of subscribers stations. at central ottlce, and metallic circuits extending between the same. means at ea h subscriber's station for making and breaking the metallic circuit, together with mnnccti e. means at the central oflice comprising the following instrumentalitics: a plurality of answering jacks less in number than the number of lines, a primary selector switch connected to each jack and containing answering terminals of a number of lines, means whereby a line calling may cause said switch to pick out its terminals and connect the same to its an swcring jack when idle, an impulse-artuated indi-ator associated with each jack. and adapted to be connected to the line calling when its jack is so connected, automatic connector switches containing calling terminals of the various lines, manually operable means including a plug for connecting a conncctor switch to an answering jack, as designated by its indicator, and relays thereby brought under control of the calling line for actuating the switch to select the line wanted, substantially as described.

13. In a telephone exchange system a plurality of subscribers stations, a central ofiioe, and metallic circuits extending between the same, means at each subscribers station for making and breaking the metallic circuit, together with connective means at the central oiiice comprising the following instrumentalities: a plurality of answering jacks less in number than the number of lines, a primary selector switch connected to each jack and containing answering terminals ,of a number of lines, means whereby a line calling may cause said switch to pick out its terminals and connect the same to its answering jack when idle, an impulse-actuated indicator associated with each jack, and adapted to be connected to the line calling when its jack is so connected, automatic connector switches containing calling terminals of the various lines, manually opc able means ineluding a plug for connecting a connector switch to an answering jack, as designated by its indicator, and relays thereby brought under control of the calling line for actuating the switch to select the line wanted, together with means for removing the indi' cator from connection with the calling line when a plug is inserted in its jack, substantially as described.

14. In a telephone exchange system sub scribers metallic circuits, with means at the substations for making and breaking the same, a common source of current and a re lay for each line. a number of answering terminals less than the number of lines, and an automatic primary selector switch associated with each tern'iinal and adapted to be controlled by the line relay of a calling line to connect the same with its terminal w hell idle,

, an indicator associated with each terminal and brought under control of: the calling line when so connected. automatic connector switches containing the calling terminals of the lines, means to connect a connector switch as designated by the indicator, to the calling line, and a supervisory signal associated with said connecting means, substantially as described.

15. In a telephone exchange system a plurality of subscribers stations and a central office with metallic line-circuits interconnecting them. each line-circuit having a relay M, a cut-oil relay N, multiple answering terminals 0, n, and calling terminals 0", together with connective means comprising the following inst-rmnentalities: a primary selector switch 0, having travelingcontacts and a circuit 9 1O, together with means to connect the same with the line contacts 0, 0, a jack J associated with the primary selector, an indicator I associated with the jack, electrcmagncts for the indicator, and a sluggish controlling relay S therefor, an automatic connector switch C, a trunk circuit; 24*25 therefor, terminating in a jack J, a plug cord-circuit for connecting the jacks J, J,

when required, and relays'having different time constants associated with the cord-circuit and responding to current chan es in a calling line to actuate and control t e connector switch, substantially as described.

16. In a telephone exchange system, subscribers stations and a central office with line circuits interconnecting them, normally disconnected answering terminals for the lines, means to connect the same in response to calls thereover, automatic connector switches containing calling terminals for the lines, means to connect any of said switches to any of the answering terminals, indicators associated with said answering terminals adapted to be controlled by the subscribers for designating the switches to be so connected, impulse sending means for actuat ng, and means for thereafter control ling the connected switches, substantially as described. v

17. In a telephone exchange system, a plurality of line circuits and substations provided with sending deyices, circuit terminals .or the lines, indicating means associated 'apparatus therefor with the terminals and adapted to be com trolled by a calling line, means for manually initiating a connection in accordance with the indications, and means controlled by said sending devices for automatically com leting the connections thereafter, substantially as described.

18. In a telephone exchange system, a plurality of subscribers lines and substations provided with sending devices, connective composed of links as follows: answering terminals, indicators associated with said terminals and adapted to be controlled b calling lines, manual connecting devices or initially connecting the lines in accordance with said indications, and

automatic switches controlled by said send ing devices to com lete the connections, substantially as described.

In testiinon whereof I allix in presence ot two witnesses.

EDWARD E. CLEMENT. Witnesses:

JAMES. H. MARR E. EnMoNsroN, 51'.

my signature 

